Fights over food ingredients have a way of spilling out into dramatic public spats: In 2012, vegetarians were crushed to find that Starbucks put insect coloring in its strawberry drinks. A year later, Chinese officials exposed a gang of lamb mongers passing off rat meat as mutton. (Cue Charlton Heston, discovering the secret protein in Soylent Green.) And now a plant vs. meat debacle has pit a Canadian news company against Subway.

The Canadian Broadcasting Corp.’s “Marketplace” news program recently had a DNA lab analyze chicken meat and strips cooked in popular fast-food chains. Subway meat, the report indicated, showed significant amounts of non-chicken DNA, in some instances more than 50 percent from soy. Chicken from other fast-food chains, such as McDonald’s and Tim Hortons, did not have such high levels of plant DNA.

Subway responded Wednesday with a prickly condemnation of the news report that suggested its chicken meat was diluted with unusually high levels of soy.

“The stunningly flawed test by ‘Marketplace’ is a tremendous disservice to our customers,” said Suzanne Greco, Subway president and chief executive, in a statement issued Wednesday night. “The allegation that our chicken is only 50 percent chicken is 100 percent wrong.”

It bolstered its response by releasing the results of its own study, commissioned in the wake of the CBC report. Subway hired two analytical laboratories to independently test pieces of the sandwich chicken from Canada, a Subway representative told The Washington Post in a statement. Maxxam Analytics in Canada and Florida’s Elisa Technologies evaluated the soy protein in the chicken samples. The plant protein was less than 10 parts per million, or below 1 percent of the sample, Subway said in Wednesday’s statement.

“These findings are consistent with the low levels of soy protein that we add with the spices and marinade to help keep the products moist and flavorful,” Subway said. It characterized the CBC report as misleading and demanded a retraction.

But the Canadian news company did not budge, either. It cited Robert Hanner, a University of Guelph biologist, who said that although DNA “cannot be taken as exact mass ratios in the product,” the genetic material could serve as a proxy for amounts of soy in the meat.

The “Marketplace” program “stands by its report,” CBC wrote in its own defense on Wednesday. It publicly posted the results of the laboratory tests, which concluded that “Subway had a much higher plant DNA percentage than the other samples.” Subway’s samples were the only ones, according to the report, that contained enough plant DNA to allow the lab to identify the soy species.

The methods of the study have not been published or made public, only the percentage results and conclusions.

DNA analyses are useful for identifying outright food fraud — like fillets of cheap Asian catfish being passed off as more expensive cod. It can also be used to detect trace biological contaminants in a sample, such as the presence of rat hair or human skin in hamburger patties.

But DNA is not traditionally used in food science to indicate percentage mass. That is, if you could separate plant matter from the meat in a chicken strip that contained, say, 50 percent bird DNA to 50 percent soy DNA, the two halves would not balance a scale.

(Cells of different organisms contain different amounts of DNA. Cells also hugely vary in mass. By way of comparison, there are thought to be about an equal number of human and bacterial cells in the human body. All of these bacterial cells, according to an August 2016 estimate, have a collective mass of 200 grams, weighing a little less than half a pound.)

Restaurants like Subway may use soy to add texture and moisten the meat. Subway’s allergen information notes its chicken may contain soy, and the chain has maintained that less than 1 percent of the protein in the chicken was soy-derived.

Subway’s chicken breast strips, according to its online listing of ingredients, include: “Boneless skinless chicken breast with rib meat, water, contains 2% or less soy protein concentrate, modified potato starch, sodium phosphate, potassium chloride, salt, maltodextrin, yeast extract, flavors, natural flavors, dextrose, caramelized sugar, paprika, vinegar solids, paprika extract, chicken broth.”

The CBC and the Natural Resources DNA Profiling & Forensic Center, which conducted the original chicken analysis in Ontario, were not able to immediately respond to a request for comment from The Washington Post.

Update: The CBC provided the following statement to The Washington Post, saying that it never claimed to show the chicken was half soy by protein as Subway had alleged.

“The tests administered for CBC were done by independent and credible experts. The tests recently circulated by Subway to the media after the episode of Marketplace aired do not address the DNA make-up of its chicken products. And, worth noting, Subway has yet to provide any explanation for the DNA test results obtained by CBC.”

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